Stages of the cell cycle
Cell division is very tightly controlled, ensuring that everything happens at the right time and in the right order. Otherwise cells can pick up faults that might lead to cancer.
This slideshow shows a cell dividing:
There are four main stages, or phases, of the cell cycle:
- “Gap 1” or G1 phase, where the cell grows in size, and checks that everything is OK for it to divide.
- “Synthesis” or S phase, where the cell copies its DNA. Find out more about how DNA is copied.
- “Gap 2” or G2 phase, where the cells checks that all its DNA has been correctly copied.
- “Mitosis” or M phase, where the cell finally divides in two. Find out more about how cells prepare to divide, then share out their DNA and split in two.
During mitosis the copied DNA is shared out equally. This means that all the chromosomes must be duplicated and separated into two full sets, one at each end of the cell that is splitting in two. The other material that makes up the cell also splits in two. The result is two identical daughter cells.
Scientists have discovered that mitosis can be broken down into four further stages:
- Prophase - when the genetic material in the cell, which is normally loosely bundled, condenses to form chromosomes. Each chromosome has duplicated and now consists of two sister chromatids.
- Metaphase - when the chromosomes align themselves along the cell spindle in the middle of the cell, ready to separate.
- Anaphase - when the sister chromatids separate and move to opposite ends of the cell.
- Telophase - when the cell prepares to split in two.
All images were kindly provided by the EM Unit at the London Research Institute and the Science Photo Library.
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